| 摘要 |
An adjustable multi-band planar antenna especially applicable in mobile terminals. A conductive element is placed in the structure of an antenna of PIFA type such that the conductive element has a significant electromagnetic coupling to the radiating plane. The parasitic element at issue is connected to a matching circuit (550) consisting of several reactive elements. The parasitic element, the matching circuit and a line (540) between them constitute an adjusting circuit of the antenna. The circuit values of the matching circuit can be chosen from at least two alternatives. Alteration in the circuit values changes the coupling between the parasitic element and the ground, in which case an operation band of the antenna is displaced, because the electric length of the antenna's part corresponding that band is changed, measured from the short-circuit point. Regarding the shiftable operation band, proper impedance matching and a proper efficiency can be arranged for the antenna. <IMAGE>
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